TD looks great, I'm sure glad you posted about it!
Not a disaster at all on the shims, just takes time. I did both methods as well with the paste, the wide and the narrow on the seem, but each gets you to the same place after sanding I learned. I ended up not taping off when I sanded, as it blended in better to the original plastic I thought. I had to repeat a few small divets a couple of times with some paste, but eventually you will fill that seem and it will be smooth like all one part! Just a pain I know. I started too with medium sandpaper to get the bulk of the paste down, then the finer and finer grit.
Dont forget that color/brand plastic spray paint I posted in the kidney shim post- when you get it sanded down to just the fine seem line that you can barely see, give it a couple of very light dustings with the paint without taping it off. Let it dry and repeat. It will transition perfectly into the original and will make your seem disappear! Your kit is AP and the color is a spot on match. The polish then is the very last step.